Canadian engineer . ing through the filtering medium, passes into thepipe arrangement below, through a rate controller into theclear water basins or to the clear water reservoir. Filtering Mediums.—The filtering mediums consist ofthree grades of gravel and one grade of sand. The gravelis of four grades, as follows: The bottom layer is threeinches thick, composed of pebbles. These pebbles passthrough a screen of one inch mesh, and are retained on ascreen of 5^ inch mesh. The second layer is two inchesthick; the grains Pass through a screen of 5^ inch mesh andare retained upon a screen of H inch
Canadian engineer . ing through the filtering medium, passes into thepipe arrangement below, through a rate controller into theclear water basins or to the clear water reservoir. Filtering Mediums.—The filtering mediums consist ofthree grades of gravel and one grade of sand. The gravelis of four grades, as follows: The bottom layer is threeinches thick, composed of pebbles. These pebbles passthrough a screen of one inch mesh, and are retained on ascreen of 5^ inch mesh. The second layer is two inchesthick; the grains Pass through a screen of 5^ inch mesh andare retained upon a screen of H inch mesh. The thirdlayer is lU inches thick, pass through a screen of ^ in.,and are retained upon a screen of 5/16 mesh. The toplayer is iH inches thick, pass through a screen of 5/16 , and are retained upon a screen having 10 meshes perlineal inch No. 20 wire. This gravel is of hard and<Jurable rounded particles, with a high specific gravity, freefrom thin or flat pieces, washed and screened, and free from. View of Groin Arches, After Removal of Forms. sand, loam, dirt and organic impurities. This gravel,without being ground or crushed, is digested for 24 hoursin cold, strong hydrochloric acid, and 95% must remaininsoluble. The filter sand is placed above the gravel, separated bya wire screen, to a depth of thirty inches, and is of a hardand durable kind, free from clay, loam, organic matter andflat particles, and stands up to a similar test as the gravelabove. This sand has an effective size of not less than•35 or more than .44 of a millimeter, and a uniform coeffic-ient of not more than Not more than 1% is finer than .25 of a millimeter, and 90% is finer than .8 of a diameter of the sand grains is computed on the spheresof equal volumes, and all percentages are calculated byweight. Clear Water Basins.—These are two in number, situatedbtlow the filters, and are 151 ft. 6 in. by 53 ft., with a con-crete groin roof that supports the filters. Th
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Keywords: ., bookcentury1800, bookdecade1890, bookpublishertoron, bookyear1893
